U.S. patent application number 11/100713 was filed with the patent office on 2006-10-12 for process for digital printing for flexible packaging.
Invention is credited to Subhankar Chatterjee, Mikhail Laksin, Jean-Dominique Turgis, Wojciech A. Wilczak.
Application Number | 20060225596 11/100713 |
Document ID | / |
Family ID | 37081912 |
Filed Date | 2006-10-12 |
United States Patent
Application |
20060225596 |
Kind Code |
A1 |
Laksin; Mikhail ; et
al. |
October 12, 2006 |
Process for digital printing for flexible packaging
Abstract
A digital printing process is disclosed comprising transferring
energy curable paste inks from a digital printing plate onto a
substrate by wet trapping, wherein said digital printing plate
comprises polymeric material covering the plate and collapsed in
areas to form a non-image area on said plate.
Inventors: |
Laksin; Mikhail; (Boonton,
NJ) ; Chatterjee; Subhankar; (Hampton, NJ) ;
Turgis; Jean-Dominique; (Vertou, FR) ; Wilczak;
Wojciech A.; (Jersey City, NJ) |
Correspondence
Address: |
KRAMER LEVIN NAFTALIS & FRANKEL LLP;INTELLECTUAL PROPERTY DEPARTMENT
1177 AVENUE OF THE AMERICAS
NEW YORK
NY
10036
US
|
Family ID: |
37081912 |
Appl. No.: |
11/100713 |
Filed: |
April 7, 2005 |
Current U.S.
Class: |
101/491 ;
101/395 |
Current CPC
Class: |
B41N 1/12 20130101; B41M
1/04 20130101; B41C 1/05 20130101 |
Class at
Publication: |
101/491 ;
101/395 |
International
Class: |
B41N 1/00 20060101
B41N001/00 |
Claims
1. A digital printing process comprising transferring energy
curable paste inks from a digital printing plate onto a substrate
by wet trapping, wherein said digital printing plate comprises
polymeric material covering the plate and collapsed areas to form a
non-image area on said plate, wherein said polymeric material
contains at least 20% air by volume in the form of a foam.
2. The process of claim 1, wherein said polymeric material is
selected from the group consisting of polyethylene, polypropylene,
polystyrene, polyester, polyurethane, polycarbonate, polyvinyl
chloride, epoxy, polyamide, polyisocyanurate, polyacrylics, rubber,
melamine and a blend thereof.
3. The process of claim 1, wherein said polymeric material is
temperature sensitive and reduces volume upon exposure to laser
beam irradiation.
4. (canceled)
5. The process of claim 1, wherein said energy curable paste ink
are UV or EB curable.
6. The process of claim 5, wherein said energy curable paste inks
are actinic irradiation curable paste inks.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to printing process for
flexible packaging.
BACKGROUND OF THE INVENTION
[0002] CTP (computer to plate and computer to press) technology is
the fastest growing segment of the printing market that is clearly
going to dominate entire pre-press across the Graphic Art field.
When CTP is applied to the offset plate, both--"to plate" and "to
press" technology already exists. The best example of "to press"
technology are Quickmaster D1, Karat etc. presses. In this case,
waterless offset plates are used. Plate imaging step is short (less
than 9 minutes for a set of 4 process colors on D1), because the
plate's layer that has to be ablated does not typically exceed 1
micron. This technology is used in commercial printing and recently
in news printing but not in flexible packaging. Selective wetting
of the plate's image and non-image areas by the ink is a very
sensitive and complex process that makes both litho and waterless
offset printing very complicated. It is even more difficult to use
offset printing on non-absorbent plastic substrates.
[0003] All these processes utilize conventional paste ink system
that have limited adhesion to plastic substrates and don't meet
most of the flexible packaging and end use requirements including
chemical and abrasion resistance, low odor, low migration and
regulatory compliance.
[0004] Ink Jet systems are said to be suitable for digital printing
on flexible substrates. However, Ink jet printing is very slow
(typically less than 100 fpm) and ink jet inks are lacking required
fitness for use typically imposed on the flexible packaging inks.
Also, UV curable ink jet inks are mostly made out of low viscosity
and low functionality acrylated monomers that have very limited
abrasion resistance, excessive odor and extractables.
[0005] Letterpress printing is much more robust because the image
area is raised over the non-image area. Print quality of
letterpress printing which utilizes higher viscosity paste inks is
equal or better than offset printing, and this technology is very
suitable for printing on flexible films or paper. Ko-Pack has a
press designed for letterpress printing or flexible substrates with
UV curable inks utilizing inter-station curing of individual
colors. This requires a very complex press design that include
individual UV lamps connected to an exhaust system and extensive
cooling of the Central Impression Drum (CID) to compensate for an
excessive heat generated by UV lamps. This significantly increases
cost of the printing press.
SUMMARY OF THE INVENTION
[0006] The present invention provides a digital printing process
comprising transferring energy curable paste inks from a digital
printing plate onto a substrate by wet trapping, wherein said
digital printing plate comprises polymeric material covering the
plate and collapsed in areas to form a non-image area on said
plate.
[0007] Other objects and advantages of the present invention will
become apparent from the following description and appended
claims.
DETAILED DESCRIPTION OF THE INVENTION
[0008] A novel printing process has been discovered and is
recommended for flexible packaging materials, said process
comprising: digital imaging of the flexible printing plate with
raised image; wet trapping multicolor printing-process with energy
curable paste inks; and instantaneous curing upon exposure to UV or
EB irradiation.
[0009] Wet trapping is a process whereby the ink layer deposited or
applied at each inking station is not dried before the next ink
layer is deposited thereover to produce a coloristic or visual
effect. More details about wet trapping techniques and inks are
provided in U.S. Pat. No. 6,772,683 which is hereby incorporated by
reference.
[0010] The plate material used in the present invention comprises a
polymer film, preferably a micro-foamed polymer film containing at
least 20% air by volume. Preferably, the polymeric film is selected
from the group consisting of polyethylene, polypropylene,
polystyrene, polyester, polyurethane, polycarbonate, polyvinyl
chloride, epoxy, polyamide, polyamide, polyisocyanurate,
polyacrylics, rubber, melamine and a blend thereof.
[0011] Upon exposure to irradiation such as IR laser beam, the
polymer film rapidly collapses forming a cavity in the non-image
area of the plate. The depth of the plate relief is controlled by
the foam size, nature of the polymer, exposure time and laser
power. Since polymer to foam ratio can be very small, the same or
similar amount of IR energy and time that are needed to ablate a
thin but hard ink receptive layer of the offset plate would cause a
significant cavity in the foamed polymer film.
[0012] It is also beneficial to use heat sensitive polymers that
would shrink at the high temperature of IR beam further increasing
the depth of the plate relief. Any ink systems can be used with
such plate, especially wet trappable EB curable paste inks which
are the most suitable to meet many end use flexible packaging
requirements.
[0013] The printing plate of the present invention allows a digital
press and printing process design for the flexible packaging market
with raised plated imaged directly on press in a very short time.
Micro-foamed plate material is a key element of this technology,
which allows an image to be sent directly to press, and the
printing plate is generated in a very short time without causing a
major press down time and printing a packaging material on selected
substrate using energy curable inks that will be ready for shipment
immediately after printing.
[0014] The proposed process will allow for the use of digital work
flow in the plate making process, shorting cycle time of the
pre-press. Simplified and less expensive printing press
configuration without interstation curing or drying will be
employed to print consecutive color from the digitally produced
flexible plate with raised image using wet trappable UV or EB
curable paste inks. Due to instantaneous cure upon exposure to UV
or EB irradiation, printing speed is limited only by the merchants
of the printing press and can reach 1000 fpm or higher.
[0015] Cured image will have sufficient chemical and abrasion
resistance to meet most of the flexible packaging requirements. EB
curable version of letterpress inks and possibly some UV
compositions will have very low odor and extractables so they can
meet all regulatory requirements, including FDA's. The whole
process is simple, computer controlled and requires limited
operator involvement. Such press and printing process can be used
not only at the flexible packaging printing plant but at
supermarket, department store, home center or any other place where
needs in small amount of unique or personalized packaging may
exist.
[0016] The invention has been described in terms of preferred
embodiments thereof, but is more broadly applicable as will be
understood by those skilled in the art. The scope of the invention
is only limited by the following claims.
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